storm-core/src/jvm/backtype/storm/hooks/IWorkerHook.java

/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package backtype.storm.hooks;

import backtype.storm.task.WorkerTopologyContext;

import java.io.Serializable;
import java.util.Map;

/**
 * An IWorkerHook represents a topology component that can be executed
 * when a worker starts, and when a worker shuts down. It can be useful
 * when you want to execute operations before topology processing starts,
 * or cleanup operations before your workers shut down.
 */
public interface IWorkerHook extends Serializable {
    /**
     * This method is called when a worker is started
     *
     * @param stormConf The Storm configuration for this worker
     * @param context This object can be used to get information about this worker's place within the topology
     */
    void start(Map stormConf, WorkerTopologyContext context);

    /**
     * This method is called right before a worker shuts down
     */
    void shutdown();
}